Search found 555 matches

by 1024MAK
15 Jul 2019 16:59
Forum: OFF TOPIC
Topic: Alan Turing to appear on new £50 note
Replies: 0
Views: 15

Alan Turing to appear on new £50 note

Alan Turing to appear on new £50 note Quoting RetroTechie from World of Spectrum forums : Great when a giant of science & technology is honored this way: https://www.bankofengland.co.uk/news/2019/july/50-pound-banknote-character-announcement Just for laughs, they should wait until the note is 6-12 m...
by 1024MAK
14 Jul 2019 19:11
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 922

Re: MTX 512 (debugging thread)

The left most voltage regulator is a 7812 and provides the +12V rail. The middle voltage regulator is a 7805 and with a TIP2955 helps provides the +5V rail. The right most device is not a voltage regulator, but a power transistor. This is a TIP2955. It boosts the current to increase the available cu...
by 1024MAK
12 Jul 2019 19:17
Forum: GENERAL DISCUSSIONS
Topic: MTX on the road.
Replies: 6
Views: 88

Re: MTX on the road.

👍 👏 8-) :D

Mark
by 1024MAK
07 Jul 2019 19:32
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 922

Re: MTX 512 (debugging thread)

The key-switches used suffer from similar problems to the keyboard switches as used on Acorn Electrons, BBC Micros and BBC Masters. The contacts inside become dirty, or a thin layer of oxide forms on the contacts. This results in either, the contacts not making electrical contact, or making intermit...
by 1024MAK
07 Jul 2019 09:15
Forum: NEW HARDWARE
Topic: ROTT 1600
Replies: 1
Views: 51

Re: ROTT 1600

Or ROTTon name :lol:

Good luck with testing :D

Mark
by 1024MAK
24 Jun 2019 15:37
Forum: PROGRAMMING
Topic: Bootstrap and boot blocks
Replies: 79
Views: 983

Re: Bootstrap and boot blocks

I’m watching this with great interest :mrgreen:

Mark
by 1024MAK
23 Jun 2019 14:30
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 922

Re: MTX 512 (debugging thread)

As the supply voltages on the 4116 DRAM chips are present and correct, then a failure of one or two of the 4116 DRAM chips is the most likely cause (assuming there is no PCB track damage). So I would not worry about looking for a short circuit on J12, as clearly no supplies are in short. Have we giv...
by 1024MAK
15 Jun 2019 15:54
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 922

Re: MTX 512 (debugging thread)

4116 DRAM chips contain 16384 memory locations. But only one bit wide. Hence in the data sheet it says the chip is a 16384 bit memory. But we need the data width to be 8 bits wide (one byte), so eight DRAM chips are needed, each DRAM chip supplies one bit of the eight bit byte. Total memory will the...
by 1024MAK
15 Jun 2019 15:30
Forum: GENERAL DISCUSSIONS
Topic: MTX 512 (debugging thread)
Replies: 48
Views: 922

Re: MTX 512 (debugging thread)

Piggy backing only works sometimes, and not very often. So I think it is not a very reliable method of testing. The problem is that DRAM chips are very complex devices and there are countless ways that they can fail. If the original fitted chip decides to output a logic low at the same time that the...
by 1024MAK
19 May 2019 16:05
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 219
Views: 6542

Re: Resurrecting an MTX500.

If the resistor is getting hot, yep, a new TIP2955 is needed.

Mark